Transmission devices known from practice and designed as automatic transmissions are constructed with shift elements for producing various gear ratios, by means of which a respective applied torque can be transmitted by friction. When the engagement of a defined gear ratio is called for, in each case one or more of the frictional shift elements is disengaged from the force flow of the transmission device, while at least one or more further frictional shift elements are engaged in the force flow of the transmission device in order to produce the gear ratio required. During the process of engaging a frictional shift element no special synchronization measures are necessary to ensure desired shifting comfort and a shift without any traction force interruption, since a desirable shift comfort level and a shift without traction force interruption can be achieved by frictional shift elements at defined contact pressures within a wide range of rotational speed differences.
In a manner known per se, since such transmission devices can only be operated with insufficient efficiencies because of drag losses that occur in the area of open frictional shift elements, certain frictional shift elements are replaced by interlocking shift elements. In such automatic transmissions made with both frictional shift elements and at least one interlocking shift element and with a corresponding gearset configuration, to carry out a defined shift command at least one interlocking shift element has to be engaged in the force flow of the transmission device.
Disadvantageously, compared with frictional shift elements interlocking shift elements with or without additional practical synchronization means can only be shifted comfortably when the speed differences are very small, i.e. close to their synchronization speed, so that the operation of a transmission device made with at least one interlocking shift element and designed as an automatic transmission is impaired to an undesired extent, at least when carrying out certain shifts in which an interlocking shift element is involved. A required shift can sometimes only be completed after the passage of an undesirably long shifting time, since before the interlocking shift element involved in the required shift can close, the speed difference in the area of the interlocking shift elements has to be adjusted to a value at which the interlocking shift element can be changed to its closed operating condition. Furthermore, in the area of an interlocking shift element no load transfer of the type that occurs with a frictional shift element is possible before reaching the closed operating condition, so shifts with interlocking shift elements cannot be carried out without interruption of the traction force.
However, additional design measures for synchronizing interlocking shift elements of transmission devices in order to enable shifts to be carried out without traction force interruption within an acceptable shifting time and with a high level of shifting comfort, increase to an undesirable extent both the manufacturing costs of the transmission devices and the structural fitting space that they occupy.